Track B is very busy and needs some breathing space, which we can get by diverting traffic onto A. Track A is the one with a less frequent service whose spare capacity we want to use. In the diagram, the two tracks are labelled A and B leading into tunnels A and B respectively. You want each source's own traffic to have priority on its own track but want to utilize spare capacity on one of the tracks because the other is getting busy. Suppose you have two tracks leading from two sources to the same location. 6 - Using presignals to allow trains to use spare tracks more intelligently Had a second train arrived on the red line, it would be able to utilise the now free platform 3rd from the right (which had cleared since the train above had entered the system).įig. However, the double-entry split signal saw that the 4th platform from the left was free as its exit signal was displaying green as the train entered the system, and therefore the train was directed to this free platform. The train currently entering in the image above must have come from the yellow line and passed the entry signal while all available platforms on the right of the double-entry split signal were occupied. This is far more efficient than forcing all 4 lines entering the station to merge into one line to be controlled by the standard RoRo layouts above. If all platforms were free then a train approaching from the bottom left would get a green on its entry signal, being directed to one of the nearest platforms, while simultaneously, a train entering the red line from the yellow side would be able to enter and go to one of the rightmost platforms - without interfering with each other thanks to the split-signal. The interesting part about this layout is that more than one train can enter the red line at the same time! The Double-Entry Split Signal is simply a combo signal that manages the whole system. This style of RoRo station allows more than one train to enter the station at once If signals C and D are red then signal E will be red preventing access to the station.īelow is an animation of how this would work in the game. If signals A and B are red then signal C will be red. If any train is between signal E and signals D and C then signal E will be red. If any train is between signal D and signals 9, 10, 11 and 12 then signal D will be red. If any train is between signal C and signals A and B then signal C will be red. If any train is between signal B and signals 5, 6, 7 and 8 then signal B will be red. If any train is between signal A and signals 1, 2, 3 and 4 signal A will be red. If signals 9, 10, 11 and 12 are red then signal D will be red. If signals 5, 6, 7 and 8 are red then signal B will be red. If signals 1, 2, 3 and 4 are red then signal A will be red. The signal E is the only Pre-signal (Entrance) Signals 1 through 12 are Pre-signal Exits 3 - An "optimal" RoRo station layout with presignals. Y turns red for northbound trains, and Y is an exit signal for X, so X turns red, which is an exit signal for AB which also turns red.įig. Here it is the other way around: A southbound train enters the single track at CD. In the meantime, an east-west train can pass through. Y is an exit signal for CD, so they both turn red for southbound trains too. X is an exit signal for Y, so Y also turns red for southbound trains. A northbound train enters the single track at AB. How it works: Call the southern entrance signals AB, the combo signals at the intersection X (south side) and Y (north side), and the northern entrance signals CD. (You can keep using normal two-way signals for the east-west line.) At the intersection, set up combo pre-signals (vertical yellow) on the north-south line. Set up entrance pre-signals (horizontal yellow) where the trains on the north-south line switch onto the single track. The problem: the signals break up the north-south section of track, meaning a northbound train could meet a southbound train at a red light at the intersection. You run the tracks across each other, and make a 4-way intersection surrounded by regular two-way signals. It can't wait for northbound and southbound trains to clear the whole single section. What if you want a new east-west track to cross the north-south track? Let's say you don't want to use a bridge, and your new east-west track is a high-speed service. You'd use regular two-way signals where the lines switch onto the single section (four in total, one for each switch). This example should give you a good idea of the help that pre-signals can be, and an example of combo signals.įor example, a line has two trains, each going to its own station.Both trains travel along a single north-south track for part of the way. Pre-signals and a single track intersection 1 Pre-signals and a single track intersection.
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